I'm not looking for any kind of augmentation explanation -- either appearance-wise or behavior-wise.
First of all, I never had an issue with the look of the Klingons magically changing between TOS and TMP without explanation; that was fine with me. In fact, I thought it was pretty cool that they changed the entire look without explanation. I suppose back then, we were much less worried about changes like that.
Secondly, I would rather them do things to give a greater understanding to the Klingon behavior as we know it from TOS/TNG/etc. I don't need them to give me a reason that their behavior was once different, then "changed", but rather give as a deeper look at Klingons that fits in well with what we already know.